This invention relates to bearings adapted to be axially movable and including a plurality of closed guideways for rolling elements, such as balls. The invention is particularly directed to bearings of this type which includes a cage for guiding the rolling elements and a thin-walled housing fitted over the cage.
In axially movable ball bearings structures of a known type, a generally tubular cage structure is povided having a plurality of closed guideways circumferentially distributed therein. Each of the guideways has a pair of axially extending guide channels, the guide channels of each pair being joined at their ends by semi-circular channels. One of the channels of each pair is open inwardly, to permit balls therein to engage a shaft. A thin-walled metal bearing housing is fitted over the cage, for example, by being forced axially over the cage. The thin-walled housing has bridge sections with courses or races engaging the balls under load, that is, the balls in the channels which are open radially inwardly. The bridge sections are joined together at the axial ends of the bearings, and the remaining channels of the cage project radially through the slots between the bridge sections.
In known ball bearing structures of this type, the thin-walled bearing housings were provided with either closed or partially slotted end rings for holding the bridge sections, and the bearing housings were hardened throughout. The hardening of the housings was effected since it is necessary for the courses or races of the bridge sections to be hardened. Since the bearing housings were hardened throughout, difficulties were occasioned in the production of the bearings. For example, the hardening of the bearing housings resulted in changes of their dimensions, as well as warping thereof. In addition, difficulties arose in the assembly of the ball bearing structure. In the normal technique for assembling the bearing, the bearing housing is pushed axially over the ball cage. In order to axially position the housing on the cage, either the cage or the bearing housing is provided with radial projections, and the bearing housing must be snapped in position with respect to these projections. As a consequence, in the assembly of the bearing housing, the housing, especially the end rings thereof, must be elastically stretched. Due to the brittleness of the end rings as a result of their hardening, however, such stretching of the housing was difficult, if not impossible.
The present invention is therefore directed to the provision of a bearing structure of the above type, wherein the thin-walled metal housing may be readily assembled over the bearing cage without danger of damage to the structure.